Preparing for the Inevitable: Digitally Preserving San Francisco's Oldest Building

The Mission San Francisco de Asís is in a race against time. Completed in 1791, the parish's Mission Dolores is the oldest building in the city, and the only intact mission established under Father Junipero Serra, the controversial Spanish Franciscan friar. In a city that's already survived two major earthquakes – in 1906 and 1989 – the inevitability of the next Big One has preservationists especially worried about this historic structure.

Mission Dolores, Church yard, Sept. 1907, courtesy of the San Francisco Historical Public Library

"It isn’t a matter of if, but when," warns Andy Galvan, curator at the Mission Dolores. Galvan is an Ohlone Indian, and his Native American ancestors lived along the coast when Spanish missionaries arrived in the 18th century. When he leads tours into the adjacent cemetery, one of the few remaining resting places that remain within city limits, he points out the markers of his great-great-great-great grandparents. They built the mission he now works in, along with his distant cousin, assistant curator Vincent Medina. The mission underwent major conservation work from 1993 to 1995, but Galvan has been unable to secure additional funds for the work he says still needs to be done before the next major quake.

Last spring, Elizabeth Lee was focused on all 21 missions on the El Camino Real, the historic 600-mile trail from San Diego to Sonoma. As operations director for CyArk, an Oakland-based nonprofit, Lee deals in lofty goals: Her organization seeks to preserve cultural heritage sites through collecting, archiving and providing open access to data gleaned via laser scanning and digital modeling. Investors in the Bay Area were willing to back the project, but it had to begin in San Francisco.

If an earthquake destroyed the mural, there would not be enough images left to reproduce it.

Lee arrived at the Mission Dolores funded and eager to start a two-day "field capture phase" late last summer. Using terrestrial scanners, a Leica C10 and the Faro Focus3D, she and her colleagues from CyArk started from the outside in, paying special attention to the cemetery which holds more than 5,000 remains, including the first native born governor of Alta California, Luis Antonio Argüello, and Charles Cora and James Casey, who were hanged by the infamous San Francisco Committee of Vigilance.

Inside, employees found an abundance of material culture and environmental data. In the attic, they encountered wood beams tied together with half-inch thick straps made from hyde. Upon closer inspection, CyArk staff noticed animal hair trapped between the straps and wood, which offered a glimpse into the building practices of the missions.

In 1791, the Ohlones painted a mural on the focal wall of the sanctuary, but just five years later an altarpiece known as a reredos was placed in front of it. The reredos, a baroque-style relief sculpture from San Blas, Mexico, successfully obscured the mural for 200 years, which depicted abstract patterns and Christian imagery. It served as an accidental conservation technique, protecting the mural from light and moisture. Archeologists Eric Blind and artist Ben Wood captured the first photos of the mural less than a decade ago, but it has yet to be fully documented. If an earthquake destroyed the mural, there would not be enough images left to reproduce it. Determined to complete the process, the CyArk field team carefully worked from above, lowering the Faro scanner into a two-foot gap between the reredos and the mural. The subsequent images, captured with laser technology, were far superior to earlier partial photographs, and Lee intends to fully archive the mural in the near future.

Perspective image of the facade at Mission Dolores created from laser scan data. Courtesy CyArk. Perspective view of the phototextured point cloud of the Mission Dolores cemetery. Courtesy CyArk.

In a little under two weeks, CyArk registered over 200 scans which were then subjected to verification, after which historic photos were layered on top. "That gives us enough to archive," Lee explains, "and now it is available for further process and additional projects, like 3D fly-through animation." CyArk has also raised funds for a forthcoming mobile app and architectural drawings.

"I hope we’ll never have to use it for reconstruction, but if we do, we’ll breathe a sigh of relief," Galvan says.

Galvan's initial goal was to prepare for the inevitable, but CyArk has also enhanced the present. Missions are at the heart of the 4th grade state-wide curriculum in public schools. The project is both revered for celebrating California history and criticized for excluding an authentic Native American narrative. Every year, over 450,000 children are assigned a mission project, but California is a big state, and a substantial number of 4th graders live far from any one of the 21 historic missions, meaning their projects must be completed with the aid of books or, realistically, the Internet. Budget cuts have further reduced the likelihood of field trips. CyArk has ensured that Galvan and Medina will be able to reach a broad audience, but Lee is quick to point out that nothing can replace the experience of visiting a heritage site. It can, however, enhance it.

"Digital technology makes a heritage site more relevant," Lee says. "In the next year, students visiting the Mission Dolores will be able to stand inside, iPad in hand, and click on the screen to pull up the view behind the reredos." They cannot see the mural with their own eyes, but they can hold it in their hand, and Galvan and Medina will be standing by, ready to tell the students how their ancestors came to paint it.